Radial arm saw with a depressible key for unlocking a switch-actuating trigger

ABSTRACT

A handtool is provided with a manipulating handle and includes a key-operated structure such that the tool cannot be operated without the key being in position in the tool. In addition, in one form of the invention the tool will not operate unless the key is depressed to a predetermined position against a force tending to return the key to the inoperative position.

United States Patent Harold R. Boteiuhr c/o Portable Electric Tools,Inc., 1200 E. State Street, Geneva, 111. 60134 Aug. 13, 1969 Dec. 7,1971 Original application Nov. 14, 1966, Ser. No. 594,084, now PatentNo. 3,482,610, dated Dec. 2, 1969. Divided and this application Aug. 13,1969, Ser. No. 849,821

Inventor Appl. No. Filed Patented RADIAL ARM SAW WITH A DEPRESSIBLE KEYFOR UNLOCKING A SWITCH-ACTUATING TRIGGER 5 Claims, 12 Drawing Figs.

US. Cl 200/42 R, 200/ 1 57 Int. Cl. 1101b 27/06, H0 l h 9/06 Field 01Search 200/42 R,

[56] References Cited UNITED STATES PATENTS 2,082,979 6/1937 SchellengerZOO/42 UX 2,735,908 2/1956 Peretti et a1. 200/157 3,104,687 9/1963 Field200/42 X FOREIGN PATENTS 909,469 3/1954 Germany 200/42 OTHER REFERENCESLatch Operated Switch"; IBM Technical Disclosure Bulletin; Vol. 8, No.5;10/196'5; by Greenfield.

Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A.Vanderhye Attorney-Hofgren, Wegner, Allen, S'tellman & McCord ABSTRACT:A handtool is provided with a manipulating handle and includes akey-operated structure such that the tool cannot be operated without thekey being in position in the tool. In addition, in one form of theinvention the tool will not operate unless the key is depressed to apredetermined position against a force tending to return the key to theinoperative position.

PATENTED [1m 7m 3 525 11 saw 1 (IF 4 IINVENTOR HAROLD RBO'TEFUHRAMTORNEYS PATENIED use nan 3,536,11

SHEET 3 [IF 4 Flea TO mm 73 4 7a 79 J @1 J0 B T7 0 i84/h Q o L87 RADIALARM SAW WITH A DEPRESSIBLE KEY FOR UNLOCKING A SWlTCII-ACTUATING TRIGGERThis application is a divisional application of my copending applicationentitled RADIAL ARM SAW filed Nov. 14, 1966, Ser. No. 594,084, now US.Pat. No. 3,482,610, issued Dec. 2, 1969 and assignedto the commonassignee G. W. Murphy Industries, Inc.

The invention relates to handtools and more particularly to the keylocking of handtools.

Radial arm saws have been known in one form or another for many years.The principal advantage generally to radial arm saws lies in the factthat the workpiece is held on a worktable while the saw is moved overand through the workpiece. Known radial arm saws have provision forperforming many different types of cuts and are adaptable for conversionfor use as a drill press, sander, grinder and the like.

The prior and current radial arm saws can be unsafe for children orpeople who are unfamiliar with power tools in general or with radial armsaws in particular. Also, current radial arm saws have awkwardly placedor inconveniently operative adjusting means for setting the angularposition of the arm relative to the worktable, for setting the angle ofthe saw blade relative to the workpiece, for guiding the vertical columnrelative to the workpiece and for guiding the horizontal position of thesaw along the arm, all of which limits the efficiency, acceptability andusefulness of the saw as a convenient home and commercial workshop tool.

It is therefore a principal object of this invention to overcome theabove-noted disadvantages of the prior art and to produce an improvedradial arm saw thereby.

It is another important object of my invention to provide an improvedkey-actuated pistol grip actuator member which prevents accidentaloperation of a power tool.

Another object of my invention is to provide an improved power toolhaving a pistol grip actuator mechanism with a key which completelydeactivates the trigger mechanism when removed.

Another object of my invention is to provide an improved power toolhaving a key means associated with a pistol grip mechanism wherein thekey means in one position in the mechanism prevents actuation of thetrigger mechanism and in a second position in the mechanism permits thetrigger mechanism to be operative.

The foregoing objects and advantages of the invention will be made clearin the following specification taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a perspective view showing my new radial arm saw with theimproved actuator key in position and with the improved adjusting meansillustrated;

FIG. 2 is an exploded perspective view of the improved radialarm-positioning and locking means;

FIG. 3 is a cross-sectional view taken on the line 3-3 of FIG. 1;

FIG. 4 is a front view, partially broken away, of the motor housing andsaw blade arbor showing the hand grip and key arrangement;

FIG. 5 is a cross-sectional view taken on the line 55 of FIG. 4;

FIG. 6 is a partial cross-sectional view of the mechanism of FIG. 5 onlywith the key depressed so that the trigger switch can operate;

FIG. 7 is a bottom view of the forward portion-of the hand actuatorshowing the work illuminating means;

FIG. 8 is a cross-sectional view through the vertical column and radialarm with the front portion of the arm taken on a plane spaced in frontof the plane of the centerline of the arm;

FIG. 9 is a partial cross-sectional view taken on the line 9- 9 of FIG.1;

FIG. 10 is an enlarged cross-sectional view of the forward portion ofthe radial arm similar to FIG. 3;

FIG. 11 is a cross-sectional view through part of the motorhousingbracket with the motor housing and hand actuator shown in full lines;and

FIG. 12 is an enlarged cross-sectional view taken on the line 12-12ofFIG. 11.

As illustrated generally in FIG. 1, a radial arm saw mechanism 20 iscomprised of a base 21 which is adapted to rest on a solid, preferablylevel surface, such as a concrete floor. The top portion of the base hasa laterally and transversely extending worktable support 22 upon whichis adjustably positioned a guide fence 25. A column support 27 is boltedto a rearwardly extending portion 28 of the base 21 and has a verticalcolumn 30 upwardly projecting therefrom. A radial arm member 32 ispivotally mounted on the top portion of the column 30. A plate 33 issecured to the bottom of arm 32, the opposite longitudinally extendingedges of the plate affording a pair of horizontally disposed tracks 33aand 33b along which is movably positioned a motor-housing bracket 35supporting a motor housing 36. Motor housing 36 includes motor assembly37 which drives a shaft from which projects the arbor member 38. A sawblade 40 is locked to the arbor 38 and has a saw blade guard 42positioned over the major portion of the blade. A handle 45 and pistolgrip mechanism 46 are connected rigidly together and with the motorhousing and are pivotally mounted about an axis transverse to the axisof the arbor shaft 38 in the lower portion of the motor housing 36 aswell be described later herein.

As shown in FIGS. ll, 3 and 8, the vertical column 30 is slidablypositioned in the column support 27 and is adapted to be telescopicallyextended into and out of said support 27 by means of the interactionbetween the screw 48 and nut 49 arrangement in the lower portion of saidsupport 27. The screw 48 is rotatably mounted in a bracket 50 in therear portion of the base 21 and has a beveled gear 51 keyed to the lowerend portion of said screw 48. For rotating; the screw 48, a horizontallydisposed rod 53 is mounted for rotation about its axis in a pair ofbearings 55 carried in brackets in said base. One portion of said rod 53has a beveled gear 56 which meshes with the beveled gear 51 on the screw48. The forward portion of the rod 53 extends through the front of thebase 21 and is keyed to a crank arm 58 projecting forwardly of said basewhereby rotation of the crank 58 in one direction will raise the column30 and its attached radial arm 32 and rotation in the opposite directionwill lower same.

The vertical column 30 has a keyway 60 formed in the rear surfacethereof. A threaded opening 61 is formed in the column member 27 inalignment with said keyway 60 in the column. A guide pin 62 having awedge-shaped forward portion 63 is slidably disposed in the opening 61in the column 27 with the wedge 63 nesting in the keyway 60 in thecolumn. A locator pin 64 projects rearwardly from the guide pin 62 andpasses through the center of a Belleville spring 65. A threaded plug 66is screwed into the opening 61 of the column with the locator pin 64 onthe guide pin 62 sliding freely in a mating aperture formed in the plug.A hexagonal head is formed on the plug 66 so that the plug 66 and guidepin 62 can be adjusted together toward the column. The wedge-shapedportion 63 of the guide pin 62 is urged into the keyway 60 of the columnby means of the compression of the Belleville spring 65 and thetightening of the plug 66 toward said column. The spring 65 provides asmall amount of resilience to the guide pin 62 so as to keep the guidepin 62 nested in the keyway 60 without a positive bind therebetween. Thecoaction between the guide pin 62 and the keyway 60 will limit, if noteliminate, the sidewise or lateral play of the arm about its pivotalaxis.

A stop 67 in the lower end of the keyway 60 is adapted to engage withthe guide pin 62 so that the column 30 cannot advance beyond apredetermined point relative to the table 22. Upon turning the crank 58on the front of the base 21, the column 30 and the radial arm 32 willraise and lower with the guide pin 62 sliding in the keyway 60 so as toprevent rotation of the column 30 about its axis. The fit is sufficientto permit the column 30 to slide axially relative to the column supportbut substantially eliminates lateral play between the column and thesupport.

The radial arm 32, as shown in FIGS. 1, 2, 3,8 and 10, has a die-castbody portion 69 which is [hollow and ribbed from below. The arm has anenlarged rear portion 70 in which is formed a cylindrical opening 711.The internal diameter of the opening 71 is such as to slidably fit aboutthe outer diameter of the column 30. The upper cylindrical portion ofthe column 30 has a segment 73 bolted thereto in a centrally locatedposition facing toward the worktable 22. The segment 73 has at leastthree vertically disposed wedge-shaped grooves 74 formed in the outersurface thereof. The middle groove 74 has its centerline extending inthe vertical plane cutting the table 21 in half while the centerlines ofthe two additional grooves 74 lie in planes which are angled 45 awayfrom the plane of the middle groove with all three planes intersectingat the centerline of the column 30. The rear enlarged portion 70 of theradial arm 32 also has a die-cast lower half or mounting member 75 whichis assembled by bolts to the portion 70 of the radial arm so as toencase the arm 32 about the segment 73 on the column 30.

As shown in FIGS. 2, 3 and 8, a pair of mating brake members 77, 78 arebolted at 79 to the inside of the mounting member 75 so as tosubstantially encircle the column 30. Brake members 77 78 are movablerelative to each other and relative to column 30 which they encircle.When the brake members are moved toward the column, they engage the samein clamping relation to lock the arm against swinging movement. Eachbrake member 77, 78 has a generally radially outwardly extending freeend 77a, 78a, respectively, which may be engaged to pinch or draw thetwo brake members together.

A radial arm-adjusting arrangement is provided in the arm for releasingor locking the arm relative to the axis of the column either inpredetermined steps or in infinite adjustments. Specifically, anelongate actuator rod 80 extends from a position just forward of thefront of the radial arm through the inner cavity of the arm to a rightangular bend 81 therein located near the rear end portion of said arm.The leg 81 of the rod that extends upwardly therefrom fits into a slot82 formed in a positioning pin 83 axially guided along the length of thearm. A forward end 84 of said pin is wedge-shaped and is adapted to fitin any one of the grooves 74 formed in the positioning segment on thecolumn. A compression spring 85 is positioned by the one web of the armand an undercut projection 86 on the rear of the pin for urging the pininto the grooves in the positioning segment.

An actuating handle 87 is mounted forward of the front of the arm inposition to be gripped and pulled toward the operator. Handle 87 isconnected to rod 80 so that outward movement of handle 87 will move therod 80 to compress the spring 85 to permit the arm to be swung about thecolumn to any desired position. Release of the handle will permit thespring to drive the pin 83 toward the segment 73 so that the forwardpart 84 of the pin will drag along the surface of the segment until itdrops into an aligned groove 74 therein.

The means for infinitely adjusting the arm relative to the column isprovided by an elongate tubular sleeve 90 slidably positioned about theouter surface of the rod 80 within the confines of the die-cast arm.Sleeve 90 has a cap member 91 having a flared cam-surfaced flange 91'fastened thereto threaded on the forward or one end of said sleeve. Theother or rear end of said sleeve is connected to a split brake actuator92 such that the split ends 920 and 92b thereof are movable toward andaway from column 30 responsive to movement of sleeve 90. Split ends 92aand 92b are generally of a size to nestably engage ends 77a, 78a of thebrake members to draw brake members 77 and 78 together when sleeve 90moves actuator 92 toward column 30 and brake members 77 and 78. Theupper surface of the sleeve has an elongate axially extending slot 93formed therein through which the upwardly extending leg 81' of the rod80 projects such that the rod 80 can be moved relative to the sleeve 90without interference therewith.

A U-shaped handle 94 is pivotally mounted on the side walls of the frontportion of the arm and has cam-shaped projections 95 formed on thebifurcated legs 96a and 96b thereof such that pivoting the handle aboutits mountings will cause the cam surfaces on the projections 95 toengage the flange member 91' on the cap member 91 of the sleeve formoving the sleeve 90 along the axis of the arm for actuating the brakemembers 77 and 78 relative to the column 30. Downward movement of thehandle 94 will release the friction brake members 77 and 78 from thecolumn. The flange member 91' is fastened to the member 91 which isthreaded on the forward end of rod and as can be seen in FIG. 2, hasnotches 98 formed around the outer circumference thereof. These notchescan be used to grip the flange 91' to rotate the flange and member 91relative to the sleeve for adjusting the operative distance between thecontact surface of the flange 91' relative to the brake members 77, 78on the column. In this way, wear or slack can be taken up withoutaffecting the operativeness of the angular adjusting means of the armrelative to the column. A cover 99 is adapted to be fastened to the,front end of the radial arm through which the handles 94 and 87project.

Means are provided for rotating the motor housing 36 relative to themotor-housing bracket 25 about an axis transverse to the length of arm32 to thereby adjust the saw blade 40 for mitering at different selectedangles. To this end, motor-housing bracket 35 includes a base plate 100which is pivoted to the motor housing 36 in a manner to be describedlater. Opposite side cover plates or frames 102a and 102b extendupwardly from either side of base plate 100 and embrace am 32 togenerally complete the bracket assembly. Each side cover plate 102a and102!) has an opening exposing the appropriate indicia along the lengthof the arm 32. An indicator is carried on each side frame to indicatethe distance the center of the blade is from the center of the column. Aplurality of track bearings 104 are secured to base plate 100 on eitherside of the bottom plate 33 of arm 32 in rolling contact with theopposite tracks 33a and 33b formed along the longitudinal edges of plate33. Preferably, these track bearings take the form of pulleylike wheels.

As best seen in FIG. 9, a lock handle 107 projects through side coverframe 102!) and is threaded through the lug 106 carried by the baseplate 100 with the threaded shank 108 of handle 107 carrying a pin 109which is in a position to abut track surface 33b of plate 33. Byloosening and tightening handle 107, the motor housing bracket 35 andmotor housing 36 may be moved and locked at selected positions along thelength of arm 32.

With particular reference to FIGS. 9 and 11, a pivot bolt 110 extendsthrough an opening 111 in plate 100 and an opening 112 in bridge portion113 of housing 36. An index plate 114 is positioned in a recess 115 inthe underside of bridge 113 and secured therein by means of machinescrew 116 (FIG. 11) which extends through one of a plurality ofpositioning openings 117 fonned in index plate 114 and into threadedopening 117' in bridge 113. Index plate 114 is also provided with aD-shaped opening 118 of a size and shape to conform to the flat portion119 formed on the threaded shank 120 of bolt 1 10.

A turning handle 121 has an end portion 122 which is threaded on boltshank 120 below index plate 114. Loosening movement of handle 121relative to bolt 110 permits a rotational movement of housing 36relative to the base plate 100 of the motor housing bracket 35, andtightening movement of handle 121 locks housing 36 against rotationalmovement relative to plate 100 of the motor-housing bracket 36. Sincehandle 121 extends through a slot in the side of the motor housing 36,its swinging movement is limited so that over a period of time the wearand set of the parts becomes such that the handle movement is not enoughto lock the motor housing 36 relative to the motor-housing bracket 35.At that time, by removing the screw 116 and rotating plate 114 and screw110 sufiicient to align the next hole 117 with the opening 117' andreinserting screw 116 will provide sufficient adjustment that themovement of the handle 121 will again lock the housing 36 relative tothe base plate 100 of the motor-housing bracket 35 This adjustment doesnot require disassembly of part of the arm as was necessary heretofore.

The rotational adjustment means further includes a lock handle 124 whichis pivoted at 125 to a portion of plate 1111) of the bracket 35. Adownwardly projecting finger 126 of handle 125 occupies one of aplurality of spaced notches 127 formed in bridge 113 of housing 36.Before housing 36 can be rotated relative to plate 1011, even afterhandle 121 is loosened, it is necessary for handle 124 to be raised sothat the finger 126 is extracted from occupation in one of the notches127. When this is done, the housing 36 may be rotated to an infinitenumber of positions of angular adjustment with respect to plate 11111 ofbracket 35 and, therefore, likewise relative to the arm 32. In thepreferred embodiment, four such notches 127 are formed so that rapidcoarse adjustment to four positions spaced 90 apart may be accomplishedsimply by swinging the housing to one of the remaining three notches 127and returning the handle 124 to the locking position.

Means are further provided for adjusting the planar disposition of thesaw blade 40 relative to the worktable 22 for bevel cutting or the like.With particular reference to FIGS. 4, 5, 11 and 12, index handle 45 towhich pistol grip 46 is secured includes an upper or support half 130aand a bottom cover half 1311!). The support half 1311a has an uprightlydisposed rounded flange portion 132 which abuts the side of housing 36adjacent opening 134 formed in the lower end of housing 36. A pivotbushing 136 is positioned in opening 134 and secured by means of capscrews 133 to the motor assembly 37 which is positioned between the legsof motor housing 36. The bushing 136 has an undercut portion 138' inwhich extends the continuous flange portion 36' of the wall of thehousing for retaining the motor assembly 37 for rotation relative to thehousing 36 about an axis perpendicular to the axis of the arbor 33. Atthe opposite end a bushing 141 with an overhanging portion 141a issecured by screws 14111 to motor assembly 37 to rotatably mount themotor with respect to an opening 1410 formed in the opposite side of themotor housing 36. In this manner, the motor assembly 37 is pivotallymounted with respect to the motor housing 36.

A brake ring 142 is positioned in the peripheral groove 144 of pivotbushing 136 by means of a pin 145 extending through the ring 142 andinto the bushing 136. The ring is split at 146 with a ball'like opening147 for receiving a wedging member such as a free-floating ball 148. Thewedging member or ball 148 is forced into the opening by movement of ahandle 150 which is threaded into the threaded opening 152 formed in theflange portion 132 on the handle 45 so that turning of the handle 150urges the wedging member of ball inwardly to spread the ring for lockingthe motor relative to the housing 36. Reverse turning of the handlepermits the resiliency of the ring and the taper of the opening 147 toforce the wedging member or ball outwardly from the beveled ball-likesplit opening 147 in brake ring 142 to release the brake and permitturning of the motor relative to the housing. Depending upon whether thewedging member or ball is pushed inwardly or permitted to move outwardlyfrom opening 146 in split 147, the brake ring 142 will expand or retractthereby tightening or loosening, respectively, the pivot bushing 136,brake ring 142 and its associated motor assembly 37 and handle 45 withrespect to the opening 134 and housing 36.

The outer periphery of bushing 136 is provided with a plurality of indexopenings 154 which are adapted to mate with the reduced beveled end 156of plunger 153. An indexing member such as a plunger 158 is urgedlaterally inwardly into the openings 154 by means of spring 160 which ispositioned behind the indexing member or plunger 158 within the sidewallof the housing 36 by means of a threaded plug 157. When handle 150 isturned to permit the wedging member or ball 143 to retract from theopening 147 and thereby loosen the bushing 136 and brake ring 142relative to the wall of the opening 134, the bushing 136, brake ring 142and the motor assembly 37 will be permitted to rotate with respect tothe bracket 36, thereby tilting blade 40. As the handle 46 is grasped toturn the motor assembly structure, the indexing member or plunger 158 iscammed outwardly from the notches 154. A plurality of such notches areformed in the periphery of the bushing 136 at predetermined locationssuch that the saw blade can be indexed to positions of standard angulardisplacement for instance along a plane at 45 and with respect to thevertical position thereof. For adjustment of the blade to an infinitenumber of angular positions between the range afforded by the spacednotches 154, the handle is merely tightened at the desired position ofangular displacement. To assist in determining the proper angularorientation, a pointer 162 is mounted on housing v36 for cooperationwith a scale 164 provided on the outer face of flange portion 132 fromwhich the reading of angular displacement of the motor assembly may beobtained.

The pistol grip portion 46 of the handle is provided with a novellocking means for preventing actuation of the saw structure. This meansis best illustrated in FIGS. 5, 6 and 11. As shown therein, handle 46includes two half pieces 1611a and 1631) which are secured together toform the unit. A switch unit is mounted interiorly of the handle means,secured to the handle half 168b. Lead wires 172 extend from the switchto a connection with the motor means (not shown) in the usual manner sothat appropriate actuation of the switch will activate the motoraccordingly. A trigger member 174 is pivoted to 166b and is linked bymeans (not shown) to switch 171) so that retraction of trigger 174actuates switch 170 to the on" position in a fashion which is typicalfor power tools in other similar electrically operated devices.

A dog 176 is pivoted at 177 to 16517 and urged by leaf spring tonormally occupy a position blocking retraction of trigger 174 so that itis impossible to retract the trigger and therefore impossible toactivate switch 170 when the dog 176 is in the position as shown in FIG.5. The dog 176 has a finger 176a which protrudes upwardly adjacent a key130 occupying a slot 182 formed in the top of the handle 46. The key hasan enlarged transversely disposed head or button 184 and a split shank155, one side 135a of the shank having an enlargement 1116 so that thekey shank 185 has a portion which is wider than slot 182.

Preferably, the key is made of a suitable yieldable material such asplastic or the like so that the key may be withdrawn from the slot bythe camming of the enlargement 186 past the relatively smaller confinesof the slot 1112, this camming facilitated by the split nature of theshank of a key. In the same manner, the key may be reinserted in theslot by the reverse movement of that required to withdraw the same. Whenso inserted, the enlargement 186 prevents accidental dislodgement orwithdrawal of the key from the slot but, as previously described, itdoes permit manual extraction of the key from the slot.

When the key is depressed by pushing on the head or the button portion1114, the enlarged side 1115a of the shank 185 on the key strikes thefinger portion 1760 of the dog and rotates the dog about the pivot 177in opposition to the influence of spring 175 to a position where the dogis out of the path of movement of the trigger 174. Then the trigger 174may be squeezed to actuate the switch, the relative positioning of thetrigger and the dog for actuation of the trigger 174 being shown in FIG.6. The handle structure is provided with the usual lock button 166 forlocking the trigger in the on position as is conventional with powersawsand the like.

Thus, in operation, to actuate the saw, the key is depressed by applyingpressure to the head or button end 184, thereby swinging the dog 176 outof its position blocking retraction of trigger 174. Trigger 1.74 is thensqueezed to retract the same and actuate switch 170, which sends anappropriate signal to the motor in the motor housing, thereby activatingthe saw. Once pressure on trigger 174 is released, it returns to theposition shown in FIG. 5; and if pressure is released from the key 1811,it also returns to the position shown in FIG. 5, with the dog 176blocking retraction of the trigger 174 and therefore preventingactuation of the device. During periods of nonuse, the key 1110 may besimply withdrawn from the slot 1112 and without the key it is impossiblefor others to activate the saw.

it is believed to be obvious that the keyoperating system just describedis not exclusively confined to a radial arm saw application. Anyelectrically operated hand device using a pressure switch can beequipped with my key system whereby the device cannot be operated eitherwithout the key or even with the key in place unless the key isdepressed to a point to deactivate the blocking means so that the devicecan be switched on and off.

The handle 45 is further provided with light means for lighting the areaof the work station. To this end, the handle is provided with a switch190 which is operatively associated with a source of power (not shown)and with light bulbs 191 which are mounted in sockets 192, see FIG. 7.The usual wiring 193 extends from the sockets to a suitable connectionwith the switch structure (not shown). The portion of the bottom coverhalf 13% of the handle 45 which underlies light bulbs 191 may beprovided with a translucent or lightly shaded,

slightly opaque panel 194 to thereby cast a diffused light ray on thearea of the worktable 22 immediately below the handle 45.

The angular position of the arm relative to a central vertical planecontaining the centerline of the column 30 and a line perpendicular tosaid centerline and also perpendicular to the fence 25 on the horizontalworktable 22 is indicated in a novel manner by means of a scale 195 andan indicator 196. The scale 195 is calibrated on the front surface of adome-shaped cap 197 snapped or screwed onto the top end portion of thecolumn 30. The position of the scale 195 lies in the plane definedabove. A cover 198 encircles the rear end portion of the radial arm 32and has a window 199 facing along the length of the arm. The indicatoror pointer 196 is screwed to the arm along its centerline so thatalignment of the pointer [96 with any number on the scale 195 willrecord the angular position of the arm 32 to the left or right of thevertical plane. The pointer 196 will sweep with the arm past the fixedscale carried by the column 30. I

The radial arm saw of this invention is both safe and convenient to use.The several controls for positioning the arm of the blade are alllocated forwardly on the structure at a point of convenient access. Theindicators for recording the angular positions of the arm, saw blade andhousing are clearly visible. In addition, the unique key which isassociated with the trigger switch for actuating the saw insures thatthe saw may not be set in motion either when the key is withdrawn fromthe opening in the hand grip or when the key is withdrawn from theopening in the hand grip or when the key is not completely depressed andheld in the depressed position. Even with the key in the slot in thehandle 45, the motor cannot be started until the key is depressed.

The foregoing detailed description has been given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as some modifications may be obvious to those skilled in theart.

I claim:

1. For use in an electric tool having a hand grip member and a switchfor actuating the electric tool, a trigger mechanism, comprising: atrigger member mounted on the handle for movement between an extendedswitch-deactuated position and a depressed switch-actuating position;means linking the trigger member to the switch so that movement of thetrigger member to the depressed switch-actuating position actuates saidswitch; means biasing said trigger member into said extended,switch-deactuated position; a trigger-locking member pivotally mountedin the handle for movement between a first and second position, saidfirst position being a triggerblocking position for preventing movementof the trigger member to the depressed switch-actuating position, and asecond position being a trigger release position permitting movement ofsaid trigger member to the depressed switch-actuating position; aremovable key adapted to be inserted through a slot in said handle, saidfirst position being an inactive position and said second position beinga depressed active position, said key being linearly movable from saidinactive position to said active position for engaginga portion of saidey with said locking member for pivoting said locking member out oftrigger-blocking position whereby said trigger member may be depressedfor actuation of said switch.

2. The apparatus of claim 1 wherein the key has a yieldable shank, theshank being slightly wider than the slot afforded in the handle so thatinsertion and extraction of the key is afforded by means of theyieldable nature of the shank.

3. The apparatus of claim 2 wherein the key has an enlargement formed onone portion of the yieldable shank, the enlargement holding the keyagainst the accidental dislodgement relative to the shank but permittingmanual insertion and withdrawal of the key from the slot.

4. The apparatus of claim 3 wherein the shank of the key is split toprovide the yieldable characteristic thereof.

5. The apparatus of claim 1 wherein the locking member is pivoted to theinterior of the handle and normally spring urged to a blocking position.

1. For use in an electric tool having a hand grip member and a switchfor actuating the electric tool, a trigger mechanism, comprising: atrigger member mounted on the handle for movement between an extendedswitch-deactuated position and a depressed switch-actuating position;means linking the trigger member to the switch so that movement of thetrigger member to the depressed switch-actuating position actuates saidswitch; means biasing said trigger member into said extended,switch-deactuated position; a trigger-locking member pivotally mountedin the handle for movement between a first and a second position, saidfirst position being a trigger-blocking position for preventing movementof the trigger member to the depressed switch-actuating position, and asecond position being a trigger release position permitting movement ofsaid trigger member to the depressed switch-actuating position; aremovable key adapted to be inserted through a slot in said handle, saidfirst position being an inactive position and said second position beinga depressed active position, said key being linearly movable from saidinactive position to said active position for engaging a portion of saidkey with said locking member for pivoting said locking member out oftrigger-blocking position whereby said trigger member may be depressedfor actuation of said switch.
 2. The apparatus of claim 1 wherein thekey has a yieldable shank, the shank being slightly wider than the slotafforded in the handle so that insertion and extraction of the key isafforded by means of the yieldable nature of the shank.
 3. The apparatusof claim 2 wherein the key has an enlargement formed on one portion ofthe yieldable shank, the enlargement holding the key against theaccidental dislodgement relative to the shank but permitting manualinsertion and withdrawal of the key from the slot.
 4. The apparatus ofclaim 3 wherein the shank of the key is split to provide the yieldablecharacteristic thereof.
 5. The apparatus of claim 1 wherein the lockingmember is pivoted to the interior Of the handle and normally springurged to a blocking position.